1. Technical Field
The invention relates to housings for electronic devices which are removably mounted on a mounting rail with a locking element positioned in the underside of the housing, whereby the locking element can be moved from a first position in which the housing is fastenable onto the rail, into a second position in which the housing can be lifted off the rail, whereby the locking element is associated with a retaining element for fixing it in the second position.
2. Description of Related Art
In view of the trend to decentralization of electronics directly into the process and the miniaturization of electronics components into compact, installation-friendly devices, more and more suitable electronics housings are needed, whereby the connection technology is generally also integrated into the housing. The individual housings are then preferably connected with one another and with a control through a bus system. The overall construction of the housing must thereby be such that a direct mounting of the housing onto the mounting rail is possible.
Depending on the respective application, this then results in a multitude of different housing types which differ in size, construction and function. All these housings are similar in that they contain electronic components, mostly in the form of integrated circuit boards, which are protected by the housing from physical contact and dirt. Such housings are generally of modular construction, whereby the housings are built especially as a kit so that the individual housing components can be quickly and individually assembled into an optimal housing. The housings often consist of a housing top and a housing base, whereby the housing top includes connectors for electrical conductors. The connectors are connected with the housing base through plug-in contacts with the housing base creating the connection to a bus system. The individual housings are thereby constructed to allow several housings to be snapped side by side onto a mounting rail so that several housings together form a housing block. The individual adjacent housings or the individual adjacent electronic apparatus can thereby preferably be electrically contacted with one another.
The fastening of such housings onto the mounting rail is achieved by way of a locking element provided in the housing base, which locking element interlocks with the mounting rail when the housing is placed on the mounting rail. In order to detach the housing, and therefore also the electronic device, from the mounting rail, the locking element, which is typically spring biased, must be retracted against its spring force.
In a known housing (xe2x80x9cPHOENIX CONTACTxe2x80x94Catalogue 10 ELEKTRONIKGEHxc3x84USExe2x80x9d 98/99, pages 46 to 49), the locking element is retracted by insertion of a screw driver tip into an especially provided access opening, so that the locking element releases the mounting rail and the electronic apparatus can be lifted off the mounting rail. It is disadvantageous thereby that the locking element must be maintained in the release position for removal of the housing or electronic device. This is especially difficult when the locking element which is located at the underside of the base is only reachable with difficulty because of space constraints. In that situation the risk exists that the inserted screw driver quickly slides out of the access opening of the locking element which results in the housing locking anew onto the mounting rail. Finally, it is hardly possible with the known housing construction to simultaneously lift several housings off the mounting rail.
A housing as described above is known from Published German Patent application DE 296 12 121, in which the locking element latches in the open position. For that purpose, the locking element, which is shaped as a slider, has two laterally positioned elastic flaps which can interlock with receptacles provided in the housing, when the slider is correspondingly pulled from the locking position into the release position. The construction of the elastic flaps is thereby problematic, since they must also hold the locking element in the closed position. Furthermore, there is the risk of the flaps being damaged or even broken off upon unseating of the locking element from the release position. If damage or breakage occurs, the locking element may then neither be latched in the release position, nor held in the locked position, so that the housing can then no longer be safely held on the mounting rail.
A quick fastening element for electronic devices is known from German Utility Model DE 79 16 477 U1, by which the devices can be snapped onto the mounting rail. The quick fastening element consists of a snap element and a wire yoke which is located in a guide in the housing base. The quick fastening element can be latched in the open position by way of the wire yoke of U-shaped construction with two opposing offsets, and by the construction of the guide with complementary shaped multi-step contours. The construction of the quick fastening element and the construction of the guide in the housing is thereby also relatively costly. Furthermore, before setting the housing onto the mounting rail, the user must again move the quick fastening element out of the release position. A similar fastening element is also known from published German Patent application DE 41 17 465 A1 and German patent DE 42 10 556 C2, whereby the construction of the fastening element and the construction of the guide in the housing is again relatively costly, and the user must again first move the fastening element manually, or with a corresponding tool, out of the release position before setting down the housing.
It is therefore one object of the present invention to overcome the disadvantages of the prior art described above.
It is yet another object of the present invention to facilitate the detachment of a housing from, and especially its setting down onto, a mounting rail, whereby the locking element is maintainable by the retaining element in the second position, i.e. the open position.
The above objects and other objects are achieved by providing a retaining element having a spring section extending essentially parallel to the locking element and a retaining section extending essentially perpendicular thereto. In the first position, the spring section is deflected against its spring force while it is relaxed in the second position. The retaining section in the first position rests with its lower edge on an edge of the mounting rail and in the second position is positioned essentially perpendicularly in front of one end of the locking element, whereby the locking element is fixed in the second position.
By constructing the retaining element in accordance with the invention, it is especially easy to hold the locking element in the second position. Such a construction of the retaining element guarantees that the latter functions essentially automatically without separate interference by a user being required. For deflection of the retaining element back into the first position, the carrier edge is used to deflected the retaining element and hold it in the deflected position, so that again no separate component is required. The housing is even somewhat additionally fastened to the mounting rail by the lower edge of the retaining section sitting on the edge of the mounting rail, since this means that the edge of the mounting rail is wedged between the lower edge of the retaining section and the end of the locking element.
Once a user has brought the locking element of the housing into the second position, i.e. the release position, a subsequent undesired re-latching of the housing onto the mounting rail is prevented by way of the retaining element. Thus, the user needs to move the locking element only once from the first position into the second position, whereafter the locking element is then maintained in the second position by the retaining element. It is therefore no longer necessary for the user to hold the locking element in the release position during lifting of the housing off the mounting rail it. The user can therefore simply lift the housing off the mounting rail with one hand. This especially provides the further possibility to simultaneously detach several housings and, thus, electronic devices, from the mounting rail.
The locking element is preferably improved by including a latch nose which grips behind an edge of the mounting rail when the locking element is in the first position. This locking element with the latch nose is, on the one hand, easily manufactured, and on the other hand, provides sufficient securing of the housing against unintended detachment. With respect to manufacturing technology, it is further advantageous when the locking element is associated with a spring element by which the locking element is pressed against the edge of the mounting rail when in the first position. On the one hand, such a spring element can be easily manufactured and on the other hand, exchange of a defective spring element is possible without exchange of the complete locking element.
It is further advantageous to construct the retaining element as a resilient metal part, whereby the retaining element can be easily produced, for example, by stamping. Furthermore, the chance of the retaining element being damaged is relatively low, since the metal part is much more robust than the flaps known from the prior art. However, should the retaining element be damaged, it can be easily replaced without exchange of the complete locking element.
According to a further preferred embodiment of the housing in accordance with the present invention, the locking element can be operated by way of an auxiliary actuator, as generally known from DE 197 24 945, whereby the auxiliary actuator is mechanically connected with the locking element. Operation of the locking element thereby means that the locking element is moved from the first position, in which the housing is fastened to the mounting rail, to the second position in which the housing can be lifted off the mounting rail. The operation of the locking element is facilitated for the user by provision of the auxiliary actuator, which preferably includes a grip portion on that end which is directed away from the locking element. Since it is necessary for functional reasons to position the locking element in the underside of the housing, it is generally accessible to the user only with relative difficulty. By providing the auxiliary actuator, it is now possible for the user to operate the locking element from a more easily accessible location, through the auxiliary actuator, for example, in the vicinity of the housing top surface.